Field of the Invention
The invention relates to closures and consists particularly in means for moving sliding doors between open and closed positions.
The Prior Art
Luther L. Bollinger, Sr. U.S. Pat. No. 3,883,992 discloses railway car side door operating structure comprising a rack extending lengthwise of and secured to a railway car side wall adjacent the door opening and an operating mechanism comprising a pair of pinions engaging the rack and manually actuated means directly mechanically connected to a pinion for rotating the pinion and thereby causing movement of the mechanism along the rack and of the door along the wall between open and closed positions. While effective to move the door, the mechanism of this patent was subject to damage because, when the door is moved rapidly along the wall and door movement ceases abruptly by contact with either the door stop during opening movements or the door jamb when closing, the kinetic energy developed in the handwheel by the rapid rotation of the pinion causes the handwheel to keep rotating like a flywheel and the torque transmitted therefrom to the pinion is frequently sufficient to strip the driving gears in the gear box or the teeth on the rack.